Hydraulic hammers are generally known to include a tool extending partially out of a housing. Such hammers may include a hydraulically actuated power cell having an impact system operatively coupled to the tool. The impact system generates repeated, longitudinally directed forces against a proximal end of the tool disposed inside the housing. The distal end of the tool, extending outside of the housing, may be positioned against rock, stone or other materials to break up those materials. During operation, the hydraulic hammer will form large pieces of broken material as well as stone dust and fine grit. The stone dust may include abrasive material, such as quartz, which could increase wear and cause premature failure of components should it migrate along the tool and into the interior of the hydraulic hammer.
Various seal arrangements have been proposed to address the issue of migrating dust. In many of these devices, the seal is positioned centrally within the housing, near the internal components of the power cell. However, other arrangements of seals and sealing strategies have been proposed, which have resulted in various levels of success in isolating the piston and internal workings of the hydraulic hammer from harmful contamination.
However, despite the presence of various seals, bushings and lubrication in a hydraulic hammer, one of the most common, most critical and most expensive failures for a hydraulic hammer is galling of the piston to the cylinder or sleeve in which the piston reciprocates. There are a number of potential causes of galling, ranging from the presence of harmful contaminants to a lack of precise machining of the piston and cylinder elements and poor quality surface finish.
One use of a hydraulic hammer is tunneling where the hydraulic hammer is used in a horizontal position. Horizontal use of a hydraulic hammer tends to cause more wear on the piston and cylinder assembly. Galling and wear would at least be reduced if it were possible to prevent the piston from mechanically touching the cylinder and if it were possible to maintain a selected clearance between them. Further, galling and wear would be reduced if it were possible to reduce the extent and magnitude of radial motion of the piston within the hydraulic hammer.
It will be appreciated that this background description has been created by the inventors to aid the reader, and is not to be taken as an indication that any of the indicated problems were themselves appreciated in the art. While the described principles can, in some respects and embodiments, alleviate the problems inherent in other systems, it will be appreciated that the scope of the protected innovation is defined by the attached claims, and not by the ability of any disclosed feature to solve any specific problem noted herein.